Spring assemblies for seat cushions, bedding and other furniture are well known. The springs are typically arranged in rows and columns to define a load supporting base. The tops of the springs, e.g., the upper terminal convolutions, are generally tied together using twine, cross-helicals and the like, or clipped to a mesh or gridwork. The lower ends, or feet, of the springs are united in a similar fashion, as in a mattress or cushion, or fixed to a framework, as in a bedding foundation. It is in the environment of a bedding foundation, i.e., box spring, that the present invention has found particular application.
A box spring generally used has a wood base frame upon which springs are mounted. Coil springs or torsion bar springs are typically used. The frame has wooden side and end rails defining its perimeter, with wood cross rails, or spans, extending between the side rails. The feet of the springs are stapled directly to the frame members.
Stapling of the springs is primarily a manual operation which depends on the skill of the worker for appropriate positioning and fixing of the springs on cross rail at the appropriate position detracts from the performance of the unit. Staples can also loosen or pull out, further impairing the performance of the unit. This method of assembly is slow and labor intensive, also requiring the use of heavy-duty staplers.
Another type of box spring assembly is disclosed in Mizelle, U.S. Pat. No. 4,470,584, which utilizes channel-shaped metal cross rails having horizontal spring mounting slots. In the '584 patent, the torsion bar springs are mounted directly to the cross rails by inserting the feet of the springs horizontally through slots running lengthwise through the sides of the cross rail. Although this method of assembly will firmly secure the spring in a consistently correct position without using staples, the twisting horizontal movement of the spring necessary for insertion is difficult to perform by automated assembly machinery, and is instead performed by hand labor. Even so, the twisting motion required for spring mounting in the '584 patent adds a measure of difficulty for the worker.